Персона: Алексеев, Павел Александрович
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Институт лазерных и плазменных технологий
Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.
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- ПубликацияТолько метаданныеInduced magnetism and “magnetic hole” in singlet ground state system PrNi(2019) Clementyev, E. S.; Lazukov, V. N.; Savchenkov, P. S.; Alekseev, P. A.; Савченков, Павел Сергеевич; Алексеев, Павел Александрович© 2019 Elsevier B.V.The phenomenon of “induced magnetic ordering” for the local magnetic moments with singlet ground state in a periodical lattice is considered for the prototype intermetallic rare-earth compound PrNi ordered ferromagnetically at temperature TC = 21 K. Within the framework of a realistic model the energy dispersion relations are obtained for the magnetic excitations above Tc along the high symmetry directions. The “soft mode” behaviour observed for the acoustic magnetic excitation along (q 0 0) direction is reproduced. The influence of the substitution of isovalent nonmagnetic La for Pr1−xLaxNi on the temperature of ferromagnetic ordering is investigated. The linear decrease of the ordering temperature TC down to zero value in increasing of the La concentration up to x = 0.5 is observed and described by the model.
- ПубликацияТолько метаданныеCooperative and Local Features of the Spin Gap Formation in the Kondo Insulators YbB12 and CeFe2Al10(2022) Lazukov, V. N.; Savchenkov, P. S.; Alekseev, P. A.; Алексеев, Павел Александрович© 2022, Pleiades Publishing, Ltd.Abstract: The formation of the excitation spectra of the ground state for Kondo insulators like YbB12, CeFe2Al10 has been studied and analyzed in terms of correspondence between cooperative and local effects. Experimental results concerning different types of substitutions for the rare earth and d-metal sublattices are discussed on the basis of model calculations. It is shown how the transformation from Kondo insulator to heavy fermions occurs in the f-electron excitation spectra of CeFe2Al10.
- ПубликацияТолько метаданныеDramatic impact of intermediate-valence impurity on induced magnetism in singlet ground state system PrNi(2020) Clementyev, E. S.; Lazukov, V. N.; Savchenkov, P. S.; Alekseev, P. A.; Савченков, Павел Сергеевич; Алексеев, Павел Александрович© 2020 Elsevier B.V.We studied the influence of La (nonmagnetic) and Ce (intermediate valence) impurities on the ferromagnetic ordering temperature Tc of compounds RE1-x(La,Ce)xNi (RE = Pr, Gd). The ordering temperature Tc was measured in a wide range of impurity concentration. Crystal electric field (CEF) splitting for the PrNi and Pr0.25Ce0.75Ni was defined by neutron spectroscopy measurements. The strong difference in the influence of La and Ce on Tc of PrNi and GdNi based systems has been obtained. The introduction of a spin-fluctuating intermediate valence impurity in PrNi leads to a dramatic increase in the area of the ordered state on the phase diagram, due to an increase in Tc, compared to the impact of La-impurity over the entire concentration range. The dependence of Tc on the Ce concentration for the Pr1-xCexNi was calculated within the framework of the model of microscopic states. The essential modification of the CEF splitting by the Ce impurity appears to be the decisive factor affecting Tc wherein the Ce ion carries zero static magnetic moments similar to the La case. The latter explains the identical dependencies of the ordering temperature on the impurity concentration observed in systems with a long-range order of local magnetic moments Gd1-xLaxNi and Gd1-xCexNi.
- ПубликацияТолько метаданныеEffect of Nd and Rh substitution on the spin dynamics of the Kondo-insulator CeFe2Al10(2020) Alekseev, P. A.; Mignot, J. M.; Adroja, D. T.; Lazukov, V. N.; Алексеев, Павел АлександровичThe dynamic magnetic properties of the Kondo-insulator state in CeFe2Al10 (spin gap, resonance mode) have been investigated using polarized neutrons on a single crystal of pure CeFe2Al10 . The results indicate that the magnetic excitations are polarized mainly along the orthorhombic a axis and their dispersion along the orthorhombic c direction could be determined. Polycrystalline samples of Nd- and Rh-doped CeFe2Al10 were also studied by the time-of-flight technique, with the aim of finding out how the low-energy magnetic excitation spectra change upon isoelectronic substitution of a rare-earth element (Nd) on the magnetic Ce site or electron doping (Rh) on the transition-element Fe sublattice. The introduction of magnetic Nd impurities strongly modifies the spin gap in the Ce dynamic magnetic response and causes the appearance of a quasielastic signal. The crystal-field excitations of Nd, studied in both LaFe2Al10 and CeFe2Al10, also reveal a significant influence of f -electron hybridization (largest in the case of Ce) on the crystal-field potential. As a function of the Rh concentration, a gradual change is observed from a Kondo-insulator to a metallic Kondo-lattice response, likely reflecting the decrease in the hybridization energy.